Risk Management Group (RMG) South Island consultant Richard White said he had conducted drug detection raids on a dozen Canterbury schools over the last year.

Schools could pay for two or four visits a year with each visit costing $200-300.

Dogs searched lockers and rooms, not students, White said.

He had seen an increase in demand for drug dogs from schools and attributed this to the prevalence of synthetic cannabis.

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Rangiora High School principal Peggy Burrows said the drug sweeps were a positive, proactive way to make the school's zero tolerance position clear.

"We wanted to show the students the sophistication of technology and dogs and how easy it is to be discovered if they were silly enough to bring drugs to school."

RMG conducted a drugs raid in October, and they would become a regular feature at the school, Burrows said.

"Over time it's creating a culture that it is never going to be acceptable. And so that's why it's going to become a regular thing."

The surprise sweep of a random sample of 20 classrooms found no drugs.

Oxford Area School contracted RMG twice last year, but principal Bob Norrish said he was yet to decide if it would become a regular activity.

"I need to look at the new search and seize legislation to see if it fits in with that."

Kaiapoi High School principal Bruce Kearney said he was unsure how effective regular random drug raids were.

"It certainly is a clear message but I don't know how effective that method is."

Kearney said the reality was, marijuana use was prevalent among teenagers.

"We need to be making sure we educate young people about making appropriate choices - because it's not necessarily the choices they make at school but rather the choices they make at parties that really impacts on them.

"When you bring drug dogs in you are subjecting all of your students to that and I'm not 100 per cent sure how effective it is, I'm no longer 100 per cent sure how legal it is."

Amuri Area School principal and Canterbury and West Coast Secondary Principals Association president Neil Wilkinson said he would not use drug dogs as drug use was not a major issue at his school.

However, he said it could be a helpful tool for schools to address drug use among students.

Lawyer Kathryn Dalziel said new search and seizure powers within the amended Education Act 1989 did not appear to sanction random drug dog searches of personal property or people.

Schools would need to tread carefully when using dog detection contractors, and ensure only school property was included in the search.

"Searching school property would be OK, as long as the dogs don't go near students' bags - that would be an illegal search."